A US judge in Nevada unsealed the documents showing some of what federal agents learned about Stephen Paddock in the week after the Las Vegas shooting.

A Las Vegas police officer stands by a blocked off area near the Mandalay Bay casino in Las Vegas. (AP File Photo)

FBI agents knew the gunman behind the deadliest mass shooting in modern US history left behind big caches of guns, ammunition and explosives when they sought warrants to search his properties and online accounts, according to court documents released Friday.

A US judge in Nevada unsealed the documents showing some of what federal agents learned about Stephen Paddock in the week after the Las Vegas shooting. Prosecutors didn’t oppose the request from media organizations, including The Associated Press, to release affidavits that were filed to get search warrants.

They also show that agents sought the email, Facebook and Instagram accounts of Paddock’s girlfriend, Marilou Danley, who was in the Philippines during the October 1 shooting.

The documents didn’t answer the key unanswered question: What motivated a 64-year-old high-stakes gambler to unleash gunfire from his room on the 32nd floor of the Mandalay Bay resort into an outdoor concert below. Paddock killed 58 people and injured hundreds more before killing himself.

Las Vegas police Officer Aden Ocampo Gomez and FBI spokeswoman Sandra Breault said Friday that they had no update about Paddock’s motive. Both called it an ongoing investigation.

Investigators have said that Paddock meticulously planned his attack and intentionally concealed his actions. He modified assault-style rifles to shoot rapidly, set up cameras to watch for police outside his hotel room and wounded a security guard in the hotel hallway.

Investigators found no evidence that Paddock had help carrying out the attack.

Paddock’s three-bedroom house in a retirement community in the city of Mesquite was searched twice — first by police and FBI agents in the hours immediately after Paddock was identified as the shooter.

Clark County Sheriff Joe Lombardo later said that October 2 search found 19 guns and several pounds of potentially explosive materials.

The FBI returned to the house a week later for what officials called “re-documenting and rechecking.”

Officers also raided Paddock’s hotel suite where he opened fire and searched his vehicle after it was found parked in the casino parking structure. Lombardo said several pounds of ammonium nitrate, a material used to make explosives, was found in the car.

Other searches were conducted at a house the gunman owned in Reno where agents found a red SUV. A neighbour reported that Paddock kept a safe the size of a refrigerator in the garage.

FBI agents also returned to that house, on October 10, after local police determined someone had broken in days earlier.

A Nevada judge is due to hear arguments Tuesday about whether Las Vegas police search warrant documents should remain sealed.